How to Overwinter Balcony Plants: A Realistic Guide for Cold Climates

Container plants are more vulnerable to winter cold than the same plants in the ground. Pots freeze solid much faster than in-ground soil. Even hardy perennials can die in containers during cold snaps. The good news: a few specific strategies prevent most winter losses.

The three categories

For overwintering planning, sort your plants into:

1. Annuals: die at first frost regardless. Compost and replace next spring.
2. Tender perennials: need to come inside or be heavily protected.
3. Hardy perennials: survive outdoors with some help.

Annuals to compost

These die when temperatures drop near freezing. No saving them.

• Tomatoes, peppers, basil (tender warm-season annuals)
• Marigolds, petunias, impatiens, most summer flowers
• Cucumbers, beans, summer squash

Pull them at first hard frost, compost the plants, save the pots and soil for spring.

Tender perennials to bring indoors

These survive winter only with indoor protection in cold climates. They include:

• Rosemary (zones 7 and colder need to bring inside)
• Lemon trees and other citrus
• Bay laurel
• Hot peppers grown as perennials
• Aloe vera and most succulents
• Geraniums (pelargoniums) – can be overwintered indoors
• Fuchsia in cold zones

The process:

1. Before first frost, prune any leggy growth.
2. Inspect for pests (don’t bring infestations indoors).
3. Move plants to a sunny window indoors.
4. Water sparingly through winter – the plant is mostly dormant.
5. Don’t fertilize until spring.
6. Move back outside after the last frost in spring, hardening off gradually.

Hardy perennials that can stay outside

These survive winter on a balcony with some protection. The catch: containers freeze more thoroughly than in-ground soil, so even a “zone 5 hardy” plant in a pot may need extra protection in zone 5.

Plants typically hardy enough for balcony overwintering:

• Hostas (most varieties)
• Heuchera
• Hardy ornamental grasses
• Sedums and sempervivums
• English ivy
• Hardy lavender (in milder zones)
• Thyme
• Hardy clematis
• Small evergreen shrubs (boxwood, juniper)

How to protect outdoor pots

1. Move to sheltered location

Pots against a wall or in a corner are warmer than pots in the open. Group them tightly.

2. Insulate the pots

Wrap the outside of the pot with bubble wrap, burlap, or specialized “pot jackets” available at garden centres. This slows the temperature swing inside the pot.

3. Mulch heavily

A 2-3 inch layer of bark, straw, or shredded leaves on top of the soil insulates roots from freeze.

4. Reduce watering

Plants use almost no water in winter. Watering excess just freezes and can damage the roots and pot.

5. Choose freeze-resistant pots

Terracotta and ceramic pots can crack in freeze cycles. Plastic, fiberglass, and resin pots handle winter much better. If you have favorite ceramic pots, empty them and store indoors for winter.

The garage / cold-frame option

For tender perennials you don’t want to bring into the heated house:

• An unheated garage stays warmer than outdoors but cold enough to keep plants dormant.
• A cold frame (a covered, insulated outdoor structure) provides similar protection.
• Even a balcony storage box covered with a tarp can work for one or two pots.

Plants in these spaces need minimal watering – check monthly. Move back outside after last frost.

Special note: terracotta pots

Terracotta cracks when wet soil inside freezes and expands. To preserve favourite terracotta pots:

1. Empty soil and dispose or save in a sealed bag.
2. Wash and dry the pot.
3. Store indoors or in a covered shed for winter.
4. Repot in spring.

Watering frozen pots

Don’t water when the soil is frozen solid – the water just sits on top until temperatures rise. If you must water in cold weather, do it on a milder day when soil is thawed enough to absorb water.

The bottom line

Overwintering container plants requires more thought than ground gardening – the pot’s exposed sides freeze fast. Annuals get composted, tender perennials come indoors, and hardy perennials get insulation and shelter. Pick freeze-resistant pots for anything staying outside. For more on container basics, see plastic vs terracotta vs ceramic pots.

The bring-everything-inside option

For cold-climate gardeners who don’t want to risk outdoor losses, bringing all tender perennials inside is the safest approach:

1. Inspect plants for pests before bringing inside (don’t import infestations).
2. Prune any leggy or damaged growth.
3. Wash leaves to remove dust and any hitchhiking insects.
4. Set up in a sunny window indoors.
5. Reduce watering through winter – they use less water indoors than outdoors.
6. Don’t fertilize until spring.
7. Watch for indoor stress (drying leaves from heated air) and adjust.

This requires space inside – usually a sunny windowsill or two. Smaller collections do well; large gardens may not have indoor space.

The garage / cold-frame middle ground

For plants too tender to leave fully outdoors but too numerous to bring inside, an unheated garage or cold frame works:

• Stays above freezing in most winters but cold enough to keep plants dormant.
• Plants need minimal watering (check monthly).
• No light requirement during dormancy.
• Moves plants outside again in spring after last frost.

Garages with attached heated houses tend to run 40-55°F in winter – perfect for dormant Mediterranean herbs, geraniums, and many tender perennials.

Outdoor protection schedule

For hardy plants staying outside, layer protection as temperatures drop:

Each protection level adds to the previous – they’re cumulative as temperatures drop further.

Watering frozen pots

One common mistake: trying to water outdoor pots in deep cold. The water just sits on top of frozen soil and doesn’t help.

• Only water on milder days (above freezing) when soil is thawed enough to absorb.
• Plants in dormancy use almost no water; don’t worry about weekly watering schedules.
• Mulched, sheltered pots can go 4-6 weeks between waterings in winter.
• Bring pots indoors briefly for watering if outdoor conditions don’t allow it.

For pot material that handles cold best, see plastic vs terracotta vs ceramic pots.